Odor stabilized lubricating oil additives



United States Patent 1 O ODOR STABILIZED LUBRICATING OIL ADDITIVES Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application July 29, 1952, Serial No. 301,609

9 Claims. (Cl. 25232.7)

This invention relates to an additive for lubricating oil to inhibit the deterioration thereof under service conditions, andwhich does not develop objectionable odors during use.

It has been proposed heretofore to react a phosphorus sulfide, such as phosphorus pentasulfide, with various hydrocarbons, including parafiins and cyclic aliphatics, for the purpose of producing a lubricating oil additive. The art recognizes that such reaction products are good additives, and in general their effectiveness can be measured, at least in part, by their sulfur content.

One of the inherent disadvantages of these additives is the development of hydrogen sulfide in an oil in which the additive has been incorporated. The objectionable odor of hydrogen sulfide renders these additives almost useless on a commercial scale for certain purposes, since the ordinary motorist will not tolerate such an odor in the oil at the time it is being added to the engine, or the development of such an odor during the use of the oil in the engines.

It is perhaps because of this inherent characteristic of such additives that the principal commercial additives are derived from organic compounds. The organic materials are relatively expensive as starting materials compared with hydrocarbon stocks. Furthermore, the manufacturers of lubricating oils are dependent upon the availability of such organic compounds from sources outside their manufacturing establishments. If a method could be developed in which the starting material for reaction with phosphorus sulfide is already available in an oil refinery, such as for instance a solvent-extracted lubricating oil, which method would provide an additive which was free from hydrogen sulfide or the development thereof, the refinery would have its own source of raw material for making a useful additive. I

Accordingly, it is an object of our invention to develop a process of preparing an additive, and to provide the additive so prepared, utilizing a hydrocarbon stock as a starting material for reaction with a phosphorus sulfide, and the subsequent treatment thereof to eliminate hydrogen sulfide therefrom and eliminate the development of hydrogen sulfide in the oil containing the additive when the oil is used under service conditions.

These results are obtained by reacting an oil of lubricating viscosity with a phosphorus sulfide in proportions and under conditions to be described subsequently. This additive has satisfactory inhibitory properties, but contains hydrogen sulfide. Even though this be eliminated from the additive, such as by blowing the additive, it has been found that when the oil containing such a purified additive is heated at an elevated temperature, such as that developed in an internal combustion engine, hydrogen sulfidedevelops and can be detected when the engine is in use. In accordance with our invention, this objectional property is obviated by treating the oil with an alkali metal hydroxide, followed by treatment with sulto be presented subsequently, that the treatment with an alkali metal hydroxide itself is not adequate, nor is the treatment with sulfur dioxide adequate. However, the treatment with both of these materials gives an eminently satisfactory product, especially when the sulfur dioxide treatment is carried out in the presence of a small amount of Water.

The oils that may be used as the starting material for the reaction product are those having a lubricating viscosity, such as 10 to 500 centistokes at 100 F. They may be acid-refined or refined by solvent extraction processes. Acid-treated oils tend to give a reaction product somewhat darker in color than the solvent-extracted oils, which is less attractive commercially but, nevertheless, possesses satisfactory inhibitory properties. Oils of high viscosity, such as SAE 70, are more difficult to handle in the reaction on account of their viscosity and are more difficult to filter. The higher viscosities also tend to give darker P ented M y 1, 19 .6

colored reaction products and are more apt to produce fur dioxide, preferably in thepresence of a small amount of water. Wehaveestablished', as will be'shown' by data sludge, which must be filtered out. Oils having a low viscosity index, such as V. I. of 70, give a product with less hydrogen sulfide initially but, on the other hand, produce additives of darker color. A study of all of the various oils has indicated that a solvent-extracted oil having an SAE 10 viscosity and a viscosity index of at least about was the optimum, considering color, ease of filtering, absence of sludge formation and other factors. It will be understood, however, that the reaction products made from all of these oils respond to the subsequent treatments which constitute our invention and that the oil will be selected depending largely upon availability, the importance of a light color and ease of handling in manufacture.

The sulfide may be any of those used in the art, such as the sesqui, the penta or heptasulfides. Phosphorus pentasulfide is readily available and it is used for this reason.

The reaction temperature between the oil and the phosphorus sulfide may be varied between about 250' and 450 F. A temperature of about 350 F. appears to be ,optimum for maximum sulfur content. Higher temperatures give additives with lower sulfur content and also give reaction products which are darker. The lower sulfur content of the product indicates a more complete reaction since there is a greater stability against the development of hydrogen sulfide. Although products prepared at a temperature of 300 to 350 F. evolve hydrogen sulfide more readily, this objection is overcome by the subsequent steps of our process, and-the lighter products obtained at this temperature are generally preferred commercially. While any temperature can be used within the range, a temperature of 300 to 350 F. is preferred, depending somewhat upon the reaction time.

The lower the reaction temperature, the longer should be the reaction time to introduce the requisite amount of sulfur, as might be expected. Higher temperatures require shorter reaction times. Regardless of the reactionftemperature, an increased reaction time darkens the additive. Increased reaction time also lowers the amount of hydrogen sulfide in the additive. The reaction time will be within a period of thirty minutes to ten hours, but for a reaction temperature of 300 F., four hours appears to be optimum, and at a temperature of 350 F. the reactiontime can be shortened to two hours.

The amount of the phosphorus sulfide reacted is also a function to some extent of the reaction time and the reaction temperature. In general, the amount may vary from 1 to 10%. Increased amounts of phosphorus sulfide result in increased sulfur concentration in the additive, especially at higher reaction temperatures and longer times. At lower temperatures, the smaller increased sulfur content of the additive dpes not jus if using larger amounts of the phosphorus sulfide. The amount preferably is within the range from 2% t and at an optimum temperature of 300 F. and a reaction period of four hours, 3.75% phosphorus pentasulfide gives a sufficiently high sulfur content in the additive to warrant not using more.

The reactions may be carried out in the manner conventional in the art using, if desired, an inert atmosphere, filtering the reaction product, blowing with air or an inert gas, and other recognized techniques of finishing the additive.

All of the additives prepared over the range of all of the variables described heretofore possess satisfactory inhibitory properties for lubricating oils, but all of them always developed hydrogen sulfide when stored in oil solution in the normal concentrations used in compounding of oils or when used under service conditions.

One method proposed for eliminating the hydrogen sulfide was to treat the additive with an adsorbent, such as activated clay. This lowered the hydrogen sulfide content and rendered it stable in storage at 150 F. up to forty hours. This stability, however, is not regarded as suflicient, since resistance to the development of hydrogen sulfide for a longer storage period is necessary the additive is added to a lubricating oil at a concentration of 5% and the oil containing the additive in this concentration heated to 150 F., it is noted that HzS develops in 16 hours. Thus this treatment does not stabilize the oil against the development of hydrogen sulfide for the requisite time. Similar conclusions are to be drawn from a comparison of the other samples.

An increase in the amount of potassium hydroxide improves the odor properties of the additive, but as the amount of potassium hydroxide is increased, the amount of sulfur in the additive is reduced. Further experimental work indicated that an amount of potassium hydroxide to eliminate the hydrogen sulfide odor completely would have lowered the sulfur content of the additive to a point of impotency. Consequently, the use of potassium hydroxide alone is unsatisfactory in preventing hydrogen sulfide formation in the additive.

It is known, of course, that sulfur dioxide reacts with hydrogen sulfide to form elemental sulfur and water, and it was thought that perhaps the treatment with sulfur dioxide would not only eliminate hydrogen sulfide from the additive but might modify the sulfur components that yield the hydrogen sulfide upon storage.

The results of treating the additive with sulfur dioxide to insure resistance to hydrogen sulfide development in are shown in Table II:

TABLE II Reac- S01 Percent Hours 1 Reae- Optical H13 in Additive to His sample on Percent 12 6 1 fig Pesrgent 3535 trlkddi- Sgnci in i0rm1g i o. a e a o ve p. eron hrs. I 2 E fP- 3832 tive p. in. Additive cent 01] at SAE 30, 95 V. I 5 1 400 NOD13 980 86. 2 2. 84 5 16 SAE 30, 95 V I- 5 1 400 3 1. 0 300 NODG 1, 450 84. 6 0) 5 16 SAE 30, 95 V I- 5 1 400 a 3. 0 300 None 1, 590 16. 2 3. 00 5 16 SAE 10, 95 3. 75 4 300 None 133 445. 9 2. 03 7. 5 16 SAE 10, 95 V. I 3. 75 4 300 4 1. 0 225 0. 25 154 61. 5 2. 27 7- 5 16 1 72 hours needed to pass this test. 2 Treated at atmospheric pressure. 3 Not measured.

4 Treated at pressure of 5 p. s. i. g.

A comparison of Samples 8, 9 and 10 shows that the sulfur dioxide treatment darkens the oil but reduces the hydrogen sulfide content of the additive. The amount of sulfur is also increased, as might be expected. A comparison of Samples 11 and 12 shows similar results. In the last sample, a small amount of water was added before the sulfur dioxide treatment, as indicated. When all of these additives were incorporated in a lubricating oil at a concentration of 5%, the oil developed an odor of hydrogen sulfide within 16 hours after storage at 150 F. The use of pressure as indicated in Sample 12 TABLE I Hours 1 Reaction Optical Percent Additive to 1118 Sample on Percent igg Temper- Percent Density g g Sulfur zf gg' Forma- No. PIS! hours a e, KOH a of m in in on tion in O F. Additive Additive I on at percent a 5 1 400 NOHB 980 86. 2 2. 84 5 16 5 1 400 1 855 38. 2 5 16 5 1 400 780 7. S 1. 47 5 16 5 4 300 None 298 152 2. 42 5 16 5 4 300 O. 9 220 5 16 2. 5 1 4.00 NODG 449 26. 2 1. 15 10 16 2. 5 1 400 0. 6 378 3. 8 0. 89 10 40 1 72 hours required to pass this test. 1 Not measure 3 Reacted at 250 F. for one hour.

A comparison of Sample No. 1 with Samples 2 and 3 shows that the use of KOH reduced the optical density, indicating a lighter color, and also reduced the amount of hydrogen sulfide in the additive. It is also be noted by a comparison of Samples 1 and .3 that the amount of sulfur in the additive is reduced by this treatment. When does not appear to affect the result, nor did the presence of water afiect the result. In the absence of any improvement whatever in odor stability, the use of sulfur dioxide by itself is impractical.

In accordance with our invention, we have discovered that the combined steps of treating the additive with potassium hydroxide and sulfur dioxide, especially in the presence of water, markedly improves the additive and gives it unusual storage-stability properties.

The potassium hydroxide, preferably in the flake form described heretofore, is reacted' with the additive at a temperature of 150to 400 F. for from one-half to five hours. Higher temperatures require shorted reaction times. Any temperatureor time which will result in the potassium hydroxide becoming absorbed is satisfactory. The amount of potassium hydroxide may vary from 0.25 to 5.0% based on the amount of the additive.

The amount of the sulfur dioxide reacted should be suificient to give the requisite stability. This may vary with the additive, the materials from which it is made and the reaction conditions under which it is made. With the optimum form of additive, the minimum amount of sulfur dioxide is about 1.9%.- The pressure of the sulfur dioxide reaction, the time and temperature of the sulfur dioxide reaction are all immaterial as long as the requisite amount of sulfur dioxide is absorbed and reacted. Generally, the pressure will be from atmospheric to about'50 lbs. per square inch gauge, and a reaction temperature of 150 to 250 F. will require a reaction time of about 4 hoursto A2 hour. There appears to be no maximum amount of sulfur dioxide to be reacted because there is a limit to the amount that can react under given "conditions.

It appears to be desirable to have a small amount of Water, generally 0.25 to 1.0%, present during the sulfur dioxide reaction to activate this reaction, although this is not essential if a longer reaction time or otherwise vigorous reaction conditions are selected.

From the data in the above table, it is apparent that the additive prepared in accordance with the invention is substantially as good as the untreated additive, in ad dition to having the very desirable property of odor stability under service conditions.

The additive may be used in any concentration to give therequisite inhibiting action depending somewhat on the properties of the base oil and the amount of inhibition. Generally the additive will be in a minor amount such as 1 to 25%, preferably about 4 to 12%. Because the additive is inexpensive and utilizes readily available and inexpensive raw materials, it can be used in larger quantities than the more expensive additives. In order to determine the effectiveness in economic terms, the additive was tested and compared with a large number of additives commercially available on the market. These were all tested in the Polyveriform test as described The results showing several optimum embodiments of in Analytic Chemistry, 21, 737 (1949). The results the invention are given in Table III. are as follows:

TABLE III (1.: I Hours 1 Reae- Reaeg 1%;? Optical ms in Percent Additive to H28 Sample on Percent tion tion Percent Percent mam in so Density Addi- Sulfur 00110.111 Forma- No. PzS5 Time, Temp., KOH5 S01 Tem Treatf of Additive, inAddi- Oil, tion in hrs. F. o tive p. p. m. tive percent Oil at F. ment 150 F.

4 300 None None 100 128.2 2. 03 7.5 16 4 300 1.0 2.2 275 0. 25 332 5.2 1.83 7.5 720 4 300 1.0 1.92 225 0. 25 170 4.4 1. 73 7.5 720 4 300 1.0 2. 63 250 0. 25 166 6.7 1.77 7.5 500 4 300 None None 112 180.7 1.99 7.5 16 4 300 1.0 2.16 225 025 154 14.3 2.01 7.5 500 4 300 1.0 2. 16 225 0. 25 154 14.3 2.01 7.5 4 500 1 72 hours needed to pass-test. 2 Reacted at 5 p. s. i. g. 3 Reaeted at 10 p. s. i. g. 4 1% water added before tested and tested at room temperature. 5 Reacted at 250 F. for one hour.

The above data clearly establish that the process of TABLE V the invention overcomes the problem of hydrogen sulfide generation on storage. In addition, it does not 111- Amou t CoStofIn terfere With the use properties of the additives under of 5; Oostin in hibitor Per service conditions. As has already been indicated, the tive Cents/Gal- 10% ot'Im- Used, 1011 of 011 f provement add1t1ve with its ob ectionable odor is a satisfactory in- Pement in Cents hibitor. As indicative of this, an additive was prepared employing the optimum conditions, namely, SAE 10 Additive oi the In- 0 4 solvent-extracted oil having a vislcfiogityf indfex 0195, rejg gfi g dfig igf 0 oru u or our ours at dditives on t e acted with 3.75% Rhosp S e Market 1 ms 1.73 to 18.2 62 to 89 I 0.265 to 2.15 300 F. This additive was incorporated in the amount I of 8% in an SAE 20 oil and the oil tested for 36 hours in the L-4 Chevrolet engine test. The results are shown in Table IV in the column headed Untreated. The same additive treated in accordance with the invention, more particularly, in 1% KOH, 0.25% water and 2.14% sulfur dioxide, was incorporated in the same amount in the same base oil and subjected to the same tests. The results are shown in Table IV, under the column marked Treated.

250 to 450 F. for from one-half to ten hours to form a lubricating oil additive, treating the additive with an alkali metal hydroxide followed by treatment with sulfur dioxide to provide an additive resistant to the development of hydrogen sulfide.

2. A method of preparing an additive which comprises reacting a mineral oil of lubricating viscosity with from 2 to phosphorus sulfide at a temperature of 250 to 450 F. for from one-half to ten hours to form a lubricating oil additive, and treating the additive with from 0.25 to 5.0% flake potassium hydroxide containing a small amount of water for one-half to five hours at 150 to 400 F., followed by treatment with sulfur dioxide in the presence of a small amount of water to absorb at least about 1.9% sulfur dioxide by weight, to provide an additive resistant to the development of hydrogen sulfide.

3. A method of preparing an additive which comprises reacting an SAE 10 solvent-extracted lubricating oil with about 3.75% phosphorus pentasulfide at a temperature of about 300 F. for about four hours to form a lubrieating oil additive, treating the additive with about 1% potassium hydroxide in flake form containing about water for about one hour at about 250 F. followed by treatment with sulfur dioxide under pressure in the presence of about 0.25% water to absorb at least about 1.9% sulfur dioxide by weight, to provide an additive resistant to the development of hydrogen sulfide.

4. The lubricating oil additive made by the process of claim 1.

5. The lubricating oil additive made by the process of claim 2. I

6. The lubricating oil additive made by the process of claim 3.

7. A lubricating oil comprising a major proportion of a mineral oil of lubricating viscosity and a minor amount to inhibit the deterioration of the oil under service conditions of an additive of claim 4.

8. A lubricating oil comprising a major proportion of a mineral oil of lubricating viscosity and a minor amount to inhibit the deterioration of the oil under service conditions of an additive of claim 5.

9. A lubricating oil comprising a major proportion of a mineral oil of lubricating viscosity and a minor amount to inhibit the deterioration of the oil under service conditions of an additive of claim 6.

References Cited in the file of this patent UNITED STATES PATENTS 2,179,711 Luten et al. Apr. 14, 1942 2,316,091 White Apr. 6, 1943 2,367,468 Mixon et al Jan. 16, 1945 2,496,508 Watson et al. Feb. 7, 1950 2,498,201 Daigle Feb. 21, 1950 2,560,546 Bartleson July 17, 1951 2,560,548 Bartleson July 17, 1951 2,637,722 Frazier May 5, 1953 

1. A METHOD OF PREPARING AN ADDITIVE WHICH COMPRISES REACTING A MINERAL OIL OF LUBRICATING VISCOSITY WITH FROM 2 TO 10% PHOSPHOROUS SULFIDE AT A TEMPERATURE OF 250 TO 450* F. FOR FROM ONE-HALF TO TEN HOURS TO FORM A LUBRICATING OIL ADDITIVE, TREATING THE ADDITIVE WITH AN ALKALI METAL HYDROXIDE FOLLOWED BY TREATMENT WITH SULFUR DIOXIDE TO PROVIDE AN ADDITIVE RESISTANT TO THE DEVELOPMENT OF HYDROGEN SULFIDE. 